The present invention relates to a control apparatus for an air conditioning system and more particularly to a control apparatus having motorized valves for an air conditioning system designed to serve a plurality of rooms at one time with its outdoor unit connected to a liquid refrigerant pipe of which is divided into a plurality of branches which are to be connected to a plurality of indoor units.
A type of control apparatus for an air conditioning system designed to control the circulation of refrigerant to indoor units by motorized valves installed in the refrigerant circuit of outdoor unit is described in Japanese Laid-Open Patent Publication No. 127055/1983. The control apparatus of the air conditioning system is designed so that the saturation temperature of suction gaseous refrigerant and the temperature of suction gaseous refrigerant are detected by temperature sensors to detect the quantity of superheat, and the detected signals are fed back to control the opening of motorized valves and adapt the cooling capacities of indoor units to variation of load and difference of piping length.
However, such a conventional control apparatus is disadvantageous in that its production cost is relatively high because it requires a complicated control circuit to enable the feedback control with PID (proportional integral and differential) control action, for example, and a refrigerant circuit with a temperature sensor.